Labor Drug Assailed
Tuesday, October 10, 2006
For the past 30 years or so, doctors have routinely given pregnant women intravenous infusions of magnesium sulfate to halt contractions that can lead to premature labor.
Now a prominent physician-researcher is calling on his colleagues to stop using the drug for this purpose, saying that the treatment is unproven, ineffective and potentially deadly -- an artifact of an earlier era when the standard of care was based more on pronouncements than on clinical trials.
The drug, sold commercially as Epsom salts and known to doctors as mag sulfate, causes side effects that range from highly unpleasant to lethal: nausea, blurred vision, headache, profound lethargy, a burning sensation and, in rare cases, life-threatening pulmonary edema, in which the lungs fill with fluid.
"Why has it persisted? Tradition," said David Grimes, vice president of biomedical affairs for the nonprofit public health group Family Health International, who co-authored the provocative commentary "Time to Quit" in the current issue of the journal Obstetrics & Gynecology.
Magnesium sulfate for preterm labor, Grimes said, is a "North American anomaly" confined to the United States and Canada whose continued use is predicated on "good hopes and good wishes rather than good data." The American College of Obstetrics and Gynecology does not endorse use of the drug for this purpose, he noted.
Four years ago a team of researchers from Australia reached similar conclusions in a report published by the Cochrane Collaboration, a respected international organization that evaluates scientific studies. The Australian team reviewed 23 clinical trials worldwide involving 2,000 women who had received the drug to quell contractions. They found that it did not reduce preterm labor and that more babies died when their mothers took the drug than in a control group where the mothers had not been given it.
Mag sulfate is typically administered between the 26th and 34th weeks of pregnancy for about 48 hours to stall contractions long enough to permit the injection of steroids, which speed fetal lung development.
Grimes said he and Kavita Nanda wrote the commentary to promulgate the Cochrane findings among the nation's OB-GYNs. "The Cochrane review hasn't received wide visibility, so that's why we wanted to put this in a journal all OB-GYNs get."
Continued use of the drug, Grimes and other critics of the practice say, exemplifies the slow pace of change in obstetrics, where it is hard to conduct clinical trials because the stakes are regarded as so high.
Doctors seeking to use a drug to stave off premature contractions that can trigger labor are better off using a calcium channel blocker such as nifedipine, which has been proven effective, Grimes said.
Grimes and Nanda estimate that about 120,000 American women receive mag sulfate each year for premature contractions, and they say some evidence suggests it may be associated with 1,900 to 4,800 fetal deaths annually in the United States. The latter figure is derived from a 1998 study in Obstetrics & Gynecology.
But jettisoning a long-standing practice in obstetrics involves factors other than evidence, some doctors say.